Arrested Tooth Germ Development of Permanent Maxillary Central Incisors – An Unusual Aetiology Shah S, Djemal S, Wong FSL Background The development of maxillary permanent central incisors may be disturbed in several ways. The most frequent causes are severe dental caries with pulpal infection of the predecessor, odontoma, supernumerary teeth or injury to the maxillary anterior region (Kobayashi et al, 1999). Other causes include dilacerated teeth, tooth malposition, crowding, retained primary incisors, dense mucoperiosteum and follicular cysts (Betts and Camilleri, 1999). The prevalence of developmental disturbance of permanent teeth secondary to primary tooth trauma is reported to be between 12%- 69% (Turgut et al, 2006). The damage to the permanent incisor can range from white or yellow-brown enamel discolourations with or without enamel hypoplasia, odontoma, crown/root dilaceration, root duplication, arrested root development, germ sequestration and in more severe cases eruption disturbances (Andreasen et al, 1971). This case report describes a history of severe trauma to the maxillary anterior region of a 3 year old girl with no apparent damage to her primary incisors yet complete arrested tooth germ development of both permanent maxillary central incisor tooth germs. Examination and history A healthy 15 year old girl was referred by her general dental practitioner regarding retained upper primary central incisors to the Paediatric Dental Department at the Royal London Dental Hospital. The patient had grown up in Ghana as a child and had sustained severe trauma at the age of 3 years to her maxillary anterior region by a rotating ceiling fan when it detached. Although the parents were present, a detailed history was difficult to obtain from them. They reported that she did sustain considerable soft tissue trauma during the accident. The patient had no other relevant medical history. Clinical examination revealed no obvious scars or abnormalities extraorally. Intraorally, she presented with both retained maxillary central primary incisors showing no signs of infection, mobility, discolouration or pain on percussion (Figs. 1 and 2). Further examination revealed hypoplastic maxillary permanent lateral incisors which had yellow-brown discolorations. The following teeth were present: Since the roots of the primary incisors were of good quality and showed no signs of root resorption, she was treatment planned for composite build-ups, combined with gingival recontouring with electrosurgery, to re- morphologise the primary central incisors to simulate permanent incisors. She will then be assessed long term for implants once her growth ceases. Discussion This case is very unusual as, although the primary incisors appear to have been spared from the trauma and show no signs of pathology, in contrast the permanent incisors appear to have been severely affected. Past literature reports that the disturbances in eruption of permanent incisors subsequent to trauma are associated with the concomitant damage to the primary predecessors. Particularly intrusive luxations of the primary incisors can lead to the disturbance in eruption of the permanent incisor (Turgut et al, 2006). However, there are no reports of these disturbances occurring without the involvement of the primary teeth. Unfortunately, it was difficult to obtain a more detailed history of the trauma and particularly what further injuries were sustained. One reason for the primary incisors remaining uninjured could be that the blade of the fan impacted above the apices of these teeth. In this case, she may have sustained a knife edge laceration sparing the primary teeth yet damaging the permanent incisor tooth germs. Brook and Winter reported on developmental arrest of permanent tooth germs following pulpal infection of primary teeth. They stated that the arrest in development can be caused by acute inflammation associated with bone resorption and tissue destruction. Once the inflammation progresses into the follicular tissues of the underlying permanent tooth germ, various degenerative and destructive changes to the ameloblasts can lead to enamel hypoplasia. In more severe cases, degeneration of the odontoblasts can result in complete disruption of dentine formation and arrested tooth germ development. Although these findings were related to the periapical infection arising from primary teeth, they also found them in cases of osteomyelitis. It is possible that these inflammatory changes followed subsequently to her trauma. Although odontodysplasia may be included as a differential diagnosis, the timing of when the trauma occurred and the degree of damage sustained appears to be stronger related to her dental condition. Treatment As the patient was concerned regarding the appearance of her small maxillary primary incisors, she was keen to have treatment. She was subsequently assessed on the combined restorative, orthodontic and paediatric multidisciplinary hypodontia clinic. Both primary central incisors possessed long root with no evidence of resorption or ankylosis and no signs of periapical pathology. Figure 1 Maxillary anterior region revealing retained deciduous central incisors with missing permanent incisors and hypoplastic lateral incisors References 1.Kobayashi H, Taguchi Y, Noda T. Eruption disturbances of maxillary permanent central incisors associated with anomalous adjacent permanent lateral incisors. International Journal of Paediatric Dentistry 1999; 9: Betts A, Camilleri GE. A review of 47 cases of unerupted maxillary incisors. International Journal of Paediatric Dentistry 1999; 9: Turgut MD, Tekcicek M, Canoglu H. An unusual developmental disturbance of an unerupted permanent incisor due to trauma of its predecessor – a case report. Dental Traumatology 2006; 22: Andreasen JO, Sundstrom B, Ravn JJ. The effect of traumatic injuries to primary teeth on their permanent successors. I. A clinicial and histiological study of 117 injured permanent teeth. Scandanavian Journal of Dental Research 1971; 79: Brook AH, Winter GB. Developmental arrest of permanent tooth germs following pulpal infection of deciduous teeth. British Dental Journal, 1975; 139: 9-11 Figure 4 Orthopantogram revealing ghost-like tooth germs of the permanent maxillary central incisors Figure 2 Extraoral view of patient The Royal London Dental Hospital Radiographic examination (Figs 3&4) showed two ghost-like tooth buds apical to the upper primary central incisors. Both buds appeared to be the arrested tooth germs of the permanent central incisors. Figure 3 Upper anterior occlusal radiograph illustrating arrested tooth germs of both central incisor